This article was co-authored by Bess Ruff, MA. Bess Ruff is a Geography PhD student at Florida State University. She received her MA in Environmental Science and Management from the University of California, Santa Barbara in 2016. She has conducted survey work for marine spatial planning projects in the Caribbean and provided research support as a graduate fellow for the Sustainable Fisheries Group.

There are 19 references cited in this article, which can be found at the bottom of the page.

You might have heard the phrase “opposites attract.” While perhaps not always the best advice for relationships, this cliché is the rule of thumb for magnet polarity. Since we inhabit a giant magnet (Earth), understanding magnet polarity on a small scale will help you understand the larger magnetic field that protects us from space radiation.[1]XResearch sourceWhether you want to label your magnets for future use or want to complete a fun science experiment, here are some easy ways to determine the polarity of your magnets.

Collect your materials. You will need only a compass and a magnet. [2]XResearch source Any type of compass will work, but a disk magnet or bar magnet will be the simplest type of magnets to use for this method.

Test your compass. While the end of the compass needle that points North is usually the red end on a typical compass, it’s a good idea to check. [3]XResearch source If you know where geographical North is from your current location, you can easily note which end of the compass needle points North.

If you are not sure where your geographic North is, you can determine which end of the compass needle is the North end by going outside at noon, when the sun is at the highest point of the sky. Hold the compass flat in your hand with the South end of the compass nearest to your body.[4]XResearch source

Note the position of the compass needle. If you live North of the Earth’s equator, the North end of the needle will be pointing towards you and the South end of the needle will be pointing toward the sun. If you live South of the equator, the South end of the compass needle will be pointing towards you.[5]XResearch source

Place your compass on a flat surface, such as a table.[6]XResearch source Be sure that the surface is free of any magnetized or metal materials that could cause a false reading. Even objects like a keychain or pocket knife can interfere with the experiment.[7]XResearch source You will notice that the North end of the compass needle is pointing to your geographical North.

Lay your magnet on the table. If you are using a disk magnet, the North and South poles will be on the two flat surfaces.[8]XResearch source If you are using a bar magnet, the poles will be on either end.[9]XResearch source

Bring your magnet next to the compass. With a disk magnet, you will need to stand the magnet on its side and hold it with your index finger so that one of the flat sides is facing your compass. [10]XResearch source

If you are using a bar magnet, place your magnet perpendicular to the compass, so that one end of the magnet is close to your compass.

Look at the compass needle. Since the compass needle is a small magnet[11]XResearch source, the South end will be attracted to the North pole of your magnet. Note that the blue end of the compass needle is South and the blue end of the magnet is North thereby attracting each other.

If the North end of the compass needle is pointing toward your magnet, you have found the South pole of your magnet. Rotate the other side of your magnet toward the compass; the South end of the compass needle will now be pointing directly to the North pole of your magnet.[12]XResearch source

Find a length of string. You can use any type of string that may be around the house, such as scrap yarn or wrapping ribbon. Your string should be long enough to tie around your magnet and suspend it.

A yard of string should be long enough in most cases. You can estimate yardage by holding the string in both hands. With your right hand, hold the string to your nose. Extend your left arm as far as possible. For most adults, the length of string between your left hand and your right hand is about a yard.

Tie your string securely around your bar magnet. Be sure that the string is tied tightly so that the magnet does not slip out of your knot. Note that if you have a disk or sphere magnet, this method is not appropriate.

Hold the string away from your body. Be sure that the magnet is free to rotate and does not come into contact with any impediments. When it stops spinning, the end that is pointing North is the North pole of the magnet. [13]XResearch source You have now created a compass!

This means that you will need to know which direction is north prior to completing the test. You can use a compass, or identify north based off of urban and topographical features in your area.

Note the difference from the compass method, wherein the South end of the compass needle is attracted to the North pole of the magnet. When using a magnet as a compass, the North pole of the magnet will point North because what we call the North pole is more accurate the “North-seeking pole,” [14]XResearch source which is attracted to the South pole of the earth’s internal magnet.[15]XResearch source

Gather materials. This method requires a few basic household objects that you likely have on hand. If you have a small magnet, a piece of Styrofoam, water, and a cup, you can complete a fun experiment that will help you determine the polarity of your magnet.[16]XResearch source

Place your magnet on the Styrofoam and put it in the water. The Styrofoam platform will turn until the North pole of your magnet is pointing North. Check a map or use a compass to determine which way is north before you start.[17]XResearch source

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Community Q&A

Place the north end of one magnet near the magnet with unknown poles. If the north end repels the magnet, that side is the unknown magnet's north pole. This obviously only works if you know the polarity of one of the two magnets.

With the aid of a bar magnet with known polarity, describe how you would determine the poles of a bar magnet with unknown poles.

Community Answer

Put them a foot apart on a flat non-metal surface. The known polarity on the left, not known on the right. Bring the right side, not known magnet closer to the left by slowly sliding it. Depending on the known polarity, you will know the other by the opposite's attraction.

wikiHow Video: How to Determine Polarity of Magnets

Tips

Any magnet for which you have already determined the North and South poles can be used to help you determine the polarity of another magnet. The South pole of one magnet will attach itself to the North pole of the other magnet. [18]XResearch source

About This Article

This article was co-authored by Bess Ruff, MA. Bess Ruff is a Geography PhD student at Florida State University. She received her MA in Environmental Science and Management from the University of California, Santa Barbara in 2016. She has conducted survey work for marine spatial planning projects in the Caribbean and provided research support as a graduate fellow for the Sustainable Fisheries Group.

The easiest way to determine the polarity of a magnet is to set the magnet on a flat surface so one of its ends is next to a compass. Then, check which end of the compass needle is pointing at the magnet. If it’s the North end, it’s pointing at the South pole of the magnet. If it’s the South end, it’s pointing at the North pole of the magnet. If you don’t have a compass, read on to learn how you can use styrofoam and water to find your magnet’s polarity instead!

Thanks to all authors for creating a page that has been read 224,037 times.

Reader Success Stories

A

Anonymous

Oct 12, 2016

"That a magnet can change the polarity of a compass was helpful. This got me thinking of ways to change middle pickup's polarity. This I need to do to create a true Humbucker sound. I have low sound at present due, I think, to all 3 pickups being same polarity."..." more

JM

Jason Mcaulay

Oct 12, 2016

"This article helped me easily and quickly determine polarity of my magnet. I noticed my compass was not true so i tried putting my magnet on a string and, sure enough, north polarity pointed north. Thank you and good luck to others."..." more

EP

Ellen Pate

Jun 6, 2017

"This article was the only place I could find to determine the north and south end of a unmarked disk magnet. It was easy to understand and follow the instructions."..." more

Rated this article:

K

Khoa

Mar 9, 2018

"Since my brother wants a compass, i taught him that method and it worked."

"That a magnet can change the polarity of a compass was helpful. This got me thinking of ways to change middle pickup's polarity. This I need to do to create a true Humbucker sound. I have low sound at present due, I think, to all 3 pickups being same polarity."..." more

JM

Jason Mcaulay

Oct 12, 2016

"This article helped me easily and quickly determine polarity of my magnet. I noticed my compass was not true so i tried putting my magnet on a string and, sure enough, north polarity pointed north. Thank you and good luck to others."..." more

EP

Ellen Pate

Jun 6, 2017

"This article was the only place I could find to determine the north and south end of a unmarked disk magnet. It was easy to understand and follow the instructions."..." more

Rated this article:

K

Khoa

Mar 9, 2018

"Since my brother wants a compass, i taught him that method and it worked."